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    Subject[PATCH 4.4 51/93] batman-adv: Fix ICMP RR ethernet access after skb_linearize
    Date
    From: Sven Eckelmann <sven@narfation.org>

    commit 3b55e4422087f9f7b241031d758a0c65584e4297 upstream.

    The skb_linearize may reallocate the skb. This makes the calculated pointer
    for ethhdr invalid. But it the pointer is used later to fill in the RR
    field of the batadv_icmp_packet_rr packet.

    Instead re-evaluate eth_hdr after the skb_linearize+skb_cow to fix the
    pointer and avoid the invalid read.

    Fixes: da6b8c20a5b8 ("batman-adv: generalize batman-adv icmp packet handling")
    Signed-off-by: Sven Eckelmann <sven@narfation.org>
    Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/batman-adv/routing.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/net/batman-adv/routing.c
    +++ b/net/batman-adv/routing.c
    @@ -359,6 +359,7 @@ int batadv_recv_icmp_packet(struct sk_bu
    if (skb_cow(skb, ETH_HLEN) < 0)
    goto out;

    + ethhdr = eth_hdr(skb);
    icmph = (struct batadv_icmp_header *)skb->data;
    icmp_packet_rr = (struct batadv_icmp_packet_rr *)icmph;
    if (icmp_packet_rr->rr_cur >= BATADV_RR_LEN)

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